1. Field of the Invention
The present invention generally relates to a development device used in an image forming apparatus such as a copier, a printer, a plotter, and a facsimile machine, and to an image forming method.
2. Discussion of the Background
In general, an electronographic image forming apparatus, for example, a copier, a printer, a facsimile machine, etc., includes an image forming mechanism for forming an electrostatic latent image, developing the latent image with toner, transferring the developed image onto a recording medium, and fixing the image thereon.
To develop the latent image, magnetic brush development devices are widely used.
A magnetic brush development roller is not conventionally equipped with an ability to transfer and agitate developer in an axial direction of the roller.
By contrast, in one known technique, by forming magnetic poles on a magnetic roller in a spiral, a magnetic brush development roller is provided with an ability to transfer developer in an axial direction of the magnetic roller.
However, this technique cannot be applied to a magnetic roller including a stationary magnet as is because it presupposes that the magnet revolves. If such a spiral structure is used in the magnetic roller including the stationary magnet, which is the most common type of magnetic roller, the quantity of the developer adhered to the magnetic roller becomes uneven in an axial direction thereof in a main polarity (or development polarity), which is undesirable.